Variable valve distributor for load-controlling a spark-ignited internal combustion engine

ABSTRACT

The invention proposes a variable valve train ( 1 ) for throttle-free load control of an internal combustion engine. Each cylinder of the internal combustion engine is provided with two inlet valves ( 9 ). According to the invention, each inlet valve ( 9 ) cooperates with a particular adjusting element ( 8, 8   a ), and the adjusting elements ( 8, 8   a ) can be actuated independently of each another. This additionally enhances the variability of the valve train.

This application is a 371 of PCT/EP00/10863 filed Sep. 20, 2001.

FIELD OF THE INVENTION

The invention concerns a variable valve train for load control of aspark-ignited internal combustion engine, said valve train beingarranged between cams of a camshaft and inlet valves of cylinders of theinternal combustion engine and comprising direct valve actuatingelements, transmission elements and adjusting elements for influencingthe lifting function of the transmission elements that are drivinglyinstalled between the cams and the valve actuating elements and havefirst working surfaces loaded by the cams and second working surfacesacting on the valve actuating elements.

BACKGROUND OF THE INVENTION

The advantages of throttle-free load control through variable or fullyvariable valve trains are sufficiently well known in the technicalfield. By dispensing with throttles, it is possible to eliminate thesuction losses that otherwise occur over a wide range of load conditionsof the internal combustion engine.

A valve train of the pre-cited type is disclosed in DE 195 09 604 A1.However, a person skilled in the art finds no information in thispublication as to how two identically operating inlet valves of a singlecylinder can be adjusted independently of each other. Thus, drawbacksare to be expected in the mixture preparation because, for example, lowloads and low rotational speeds result in a too feeble turbulence of thecharge. In the described state of the internal combustion engine, thetoo feeble turbulence can lead to a precipitation of fuel upon expansionof the cylinder charge when the inlet valve has closed. On the otherhand, a large gas exchange cross-section would be desirable at highspeeds of rotation and high loads because it creates a tumble streamthat favors high performance. Thus, seen as a whole, the generic valvetrain does not possess sufficient variability.

OBJECT OF THE INVENTION

The object of the invention is therefore to provide a valve train of thepre-cited type that is distinctly more variable and, at the same time,relatively simple to operate.

SUMMARY OF THE INVENTION

The invention achieves the above object in that each cylinder possessesat two inlet valves (9), and at least one particular part of thetransmission element comprising the second working surface (13) and oneparticular element (8,8 a) are associated to each inlet valve (9), saidparticular adjusting element (8,8 a) being displaceable relative to afurther adjusting element (8,8 a) of a second inlet valve (9) or tofurther adjusting elements of further inlet valves of each cylinder.

Accordingly, each cylinder possesses at least two inlet valves, and atleast one particular part of the transmission element comprising thesecond working surface and one particular adjusting element areassociated to each inlet valve, said particular adjusting element beingdisplaceable relative to a further adjusting element or to furtheradjusting elements of further inlet valves of each cylinder.

With these measures, the initially described drawbacks are eliminated.All the inlet valves (advantageously two) of each cylinder can beadjusted independently of one another. Thus, it is possible, forexample, that during idle running, one gas exchange valve is completelyshut off and the other executes only a low lift. In this way, theturbulence of the charge can be infinitely influenced so that theaforesaid drawbacks are effectively eliminated. The variability of theentire valve train becomes very similar to that of an electromagneticvalve timing control with which each gas exchange valve can be regulatedindividually.

According to a first embodiment of the invention, the adjusting elementsthat are configured, for instance, as pivoting fingers or eccentricsextend on telescopically inter-inserted shafts (hollow shaft and furthershaft). The hollow shaft is rigidly connected to the adjusting elementsof a first row of identical inlet valves of all the cylinders and thefurther shaft is rigidly connected to the adjusting elements of afurther row of adjacent, identical inlet valves of all the cylinders,the shafts, together with the adjusting elements being rotatablerelative to each other. In this way, it is no longer necessary toactuate the different adjusting elements of each cylinder separately.

A further conceivable solution that is explicitly included in the scopeof the invention concerns an embodiment in which it is not the inletvalves of each cylinder that are controlled independently of one anotherbut the inlet valves of at least two cylinders that can be actuateddifferently from each other. This means that all the adjusting elementsof one particular cylinder are connected to the hollow shaft and all theadjusting elements, for instance, of an adjacent cylinder are connectedthrough entraining elements to the further shaft that extends within thehollow shaft. This configuration thus makes it possible to shut off acylinder. Thus, one cylinder can be deactivated while a valve lift takesplace at another cylinder.

The adjusting elements may also be configured as eccentrics and appliedin accordance with the solution of the aforesaid document DE 195 09 604A1. However, it is also possible to configure the adjusting elements aspivoting fingers as illustrated in the appended drawing.

Segment-shaped slots in the hollow shaft for the entraining elements ofthe adjusting elements of the further row of identical inlet valves atthe same time define a maximum angle of relative rotation of theadjusting elements.

According to a further sub-claim, the adjusting elements of the hollowshaft are fixed thereon in a simple manner by an interference fit. Thefurther adjusting elements are fixed on the further shaft, for instance,by an entraining element configured as a pin. Here, too, it is possibleto use an interference fit or a screw connection and the like.

According to a further advantageous feature of the invention, the hollowshaft and the further shaft can be actuated separately. For thispurpose, an electric or hydraulic actuator is arranged on a front end ofeach shaft. However, it is also possible to provide inter-insertedactuators only on one end of the shafts.

In a preferred embodiment of the invention according to a furthersub-claim, the separate adjusting elements are arranged on aratchet-type valve train whose transmission elements are made up of twoparts. The adjusting elements are configured as pivoting fingerscomprising a scanning contour that is scanned during cam lift by a partof the transmission element configured as a ratchet.

Finally, it is proposed to use a finger lever as a valve actuatingelement. However, it is both conceivable and within the scope of theinvention to use oscillating levers or rocker arms, and also cuptappets.

It is expressly stated that the scope of the intention does not extendonly to a valve train as described in accordance with the appendeddrawing but also to valve trains comprising an adjusting means asdisclosed, for example, in the aforesaid generic document DE 195 09 604A1.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be described more closely with reference to theappended drawing.

FIG. 1 is a schematic view of a variable valve train,

FIG. 2 shows an adjusting element configured as pivoting finger, for thevalve train of FIG. 1, and

FIG. 3 is a longitudinal section through the shafts for mounting theadjusting elements.

DETAILED DESCRIPTION OF THE DRAWING

FIG. 1 discloses a variable valve train 1, the basic principle and modeof functioning of which are known in the technical field. The valvetrain 1 serves for load control of a spark-ignited internal combustionengine and is fully variable. This figure shows a cam 2 of a camshaft 3that acts on a first working surface 4 (roller) of a two-parttransmission element 5 that is configured on its cam-proximate side as alever 5 a. This lever 5 a is mounted approximately centrally on a hollowshaft 6 (see also FIG. 3). The hollow shaft 6 surrounds a further shaft7 for relative rotation thereto. An adjusting element 8 is disposed on along side of the lever 5 a. This adjusting element 8 serves to influencethe lift of a first row of identical inlet valves 9 of the cylinders.The adjusting element 8 is fixed on the hollow shaft 6 by a press fitand comprises a scanning contour 9 a situated opposite the ratchet 5 b.

The ratchet 5 b is fixed on a fulcrum 11 situated on an end 10 oppositefrom the first working surface 4 of the lever 5 a. The ratchet 5 b canpivot relative to the fulcrum 11 and comprises a third working surface12 which is configured as a roller and cooperates with the scanningcontour 9 a. The ratchet 5 b further comprises a second working surface13 oriented away from the third working surface 12. The second workingsurface 13 acts on a contact surface 14 (roller) of a direct valveactuating element 15. This direct valve actuating element 15 isconfigured in the present example of embodiment as a finger lever thatis mounted at one end on a support element 16 and acts at the other endin lifting direction on the inlet valve 9.

When a cam lift causes the lever 5 a to pivot together with the ratchet5 b, this latter is forced to move in a channel situated between thescanning contour 9 a and the contact surface 14. In the angular positionof the adjusting element 8 shown in FIG. 1, this produces a maximum lifton the inlet valve 9. The movement imparted to the ratchet 5 b istherefore composed of a movement of rotation about the fulcrum 11 and amovement of translation in the aforesaid channel.

For obtaining a desired zero lift of the inlet valve 9, for instance,the adjusting element 8 is rotated in anti-clockwise direction by arotation of the hollow shaft 6 effected by an actuator, not specified,that is arranged on an end of the hollow shaft 6. This anti-clockwiserotation of the adjusting element 8 is continued till the third workingsurface 12 of the ratchet 5 b traverses only a fore-positioned basecircle segment of the scanning contour 9 a. Thus, the ratchet 5 b doesnot pivot in opening direction of the inlet valve 9 and this remainsclosed.

FIGS. 2, 3:

However, the valve train is to be designed for at least two inlet valvesfor each cylinder. Each inlet valve 9 then has its own transmissionelement 5 at least in the region of the ratchet 5 b. Each ratchet 5 b isassociated to a separate adjusting element 8, 8 a so that the two inletvalves 9 of each cylinder can be adjusted independently of each other(see also discussion of advantages in connection with the claims).

For this purpose, as mentioned above, the hollow shaft 6 houses arelatively rotatable further shaft 7 in its bore 17. The hollow shaft 6and the further shaft 7 can be actuated by actuators operatingindependently of each other. It is conceivable to arrange one actuatorat one end of the shafts 6, 7 and a further actuator at the other end ofthe shafts 7, 6. It is conceivable, for instance, to use hydraulic,electric or electro-hydraulic and similar measures.

As disclosed in FIG. 3, all the adjusting elements 8 of a first row ofinlet valves 9 of the cylinders are pressed onto the hollow shaft 6. Theadjusting elements 8 a of a further row of identical inlet valves 9 ofall the cylinders are rigidly connected to the further shaft 7. For thispurpose, the further shaft 9 comprises a segment-shaped slot 18 in theregion of the adjusting elements 8 a. An entraining element 19configured in the present embodiment as a pin projects through this slot18. The entraining element 19 is fixed both in a reception 20 of thefurther shaft 7 and in a reception 21 of the adjusting element 8 a.These measures permit the two inlet valves 9 of each cylinder to bedisplaced independently of each other. Thus, for example, at low speedsof rotation and loads one inlet valve 9 can be completely shut off orexecute only a minimum lift. The other inlet valve 9 then remains openin a “normal” manner so that a strong turbulence that promotes mixturebuild-up is produced in the cylinder.

It goes without saying that it is also conceivable to use the measuresproposed by the invention for influencing even three inlet valves percylinder independently of one another. In this case, the further shaft 7would have to receive still another shaft in its interior and beprovided with additional entraining elements that would project throughthe further shaft 7 as well as the hollow shaft 6.

Seen as a whole, therefore, a valve train is created that not onlyincludes the advantages of known variable mechanical systems but alsopossesses an enhanced variability that further approaches thevariability of electromagnetic valve trains.

List of reference numerals  1 Valve train  2 Cam  3 Camshaft  4 Firstworking surface  5 Transmission element  5a Lever  5b Ratchet  6 Hollowshaft  7 Further shaft  8 Adjusting element (pivoting finger)  8aAdjusting element (pivoting finger)  9 Inlet valve  9a Scanning contour10 End 11 Fulcrum 12 Third working surface 13 Second working surface 14Contact surface 15 Direct valve actuating element (finger lever) 16Support element 17 Bore 18 Slot 19 Entraining element 20 Reception 21Reception

1. A variable valve train (1) for load control of a spark-ignitedinternal combustion engine, preferably a fully variable valve train (1)for throttle-free load control of the internal combustion engine, saidvalve train (1) being arranged between cams (2) of a camshaft (3) andinlet valves (9) of cylinders of the internal combustion engine andcomprising direct valve actuating elements (15), transmission elements(5) and adjusting elements (8, 8 a) for influencing the lifting functionof the transmission elements (5) that are drivingly installed betweenthe cams (2) and the valve actuating elements (15) and have firstworking surfaces (4) loaded by the cams (2) and second working surfaces(13) acting on the valve actuating elements (15), characterized in thateach cylinder possesses at least two inlet valves (9), and at least oneparticular part of the transmission element (5) comprising the secondworking surface (13) and one particular adjusting element (8, 8 a) areassociated to each inlet valve (9), said particular adjusting element(8, 8 a) being displaceable relative to a further adjusting element (8,8 a) of a second inlet valve (9) or to further adjusting elements offurther inlet valves of each cylinder, the adjusting elements (8) arepivoting fingers or eccentrics and are mounted on a hollow shaft (6)that extends in direction of the inlet valves (9), the adjustingelements (8) of a first row of identical inlet valves (9) of allcylinders are fixed to the hollow shaft (6) by a rigid connection, andwhen two inlet valves (9) are provided for each cylinder, the adjustingelements (8 a) of a further row of adjacent identical inlet valves (9)of all cylinders are rotatably mounted relative to the hollow shaft (6),a further shaft (7) is arranged in a bore (17) of the hollow shaft (6)for relative rotation thereto, which further shaft (7) comprises anentraining element (19) for each adjusting element (8 a) of the furtherrow of identical inner valves (9), and said entraining element (19)projects through the hollow shaft (6) and is connected to the associatedadjusting elements (8 a).
 2. A valve train according to claim 1,characterized in that, the hollow shaft (6) comprises in the region ofeach projecting entraining element (19), a segment-shaped slot (18), theentraining element (19) is configured as a pin or similar to a pin or asa screw and extends on one side in a reception (20) of the further shaft(7) and on another side in a reception (21) of the associated adjustingelement (8 a).
 3. A valve train according to claim 2, characterized inthat the slot (18) describes an are that defines a desired maximumangular displacement of the adjusting elements (8) for the first row ofinlet valves (9) relative to the adjusting elements (8 a) for thefurther row of inlet valves (9).
 4. A valve train according to claim 1,characterized in that the rigid connection of the adjusting elements (8)to the hollow shaft (6) is effected by an interference fit.
 5. A valvetrain according to claim 1, characterized in that each of the hollowshaft (6) and the farther shaft (7) has a separate electric or hydraulicactuator.
 6. A valve train according to claim 5, characterized in thatthe actuators are arranged on opposite ends of the shafts (6, 7).
 7. Avalve train according to claim 1 wherein the valve actuating elements(15) are finger levers.
 8. A variable valve train (1) for load controlof a spark-ignited internal combustion engine, preferably a fullyvariable valve train (1) for throttle-free load control of the internalcombustion engine, said valve train (1) being arranged between cams (2)of a camshaft (3) and inlet valves (9) of cylinders of the internalcombustion engine and comprising direct valve actuating elements (15),transmission elements (5) and adjusting elements (8, 8 a) forinfluencing the lifting function of the transmission elements (5) thatare drivingly installed between the cams (2) and the valve actuatingelements (15) and have first working surfaces (4) loaded by the cams (2)and second working surfaces (13) acting on the valve actuating elements(15), characterized in that each cylinder possesses at least two inletvalves (9), and at least one particular part of the transmission element(5) comprising the second working surface (13) and one particularadjusting element (8, 8 a) are associated to each inlet valve (9), saidparticular adjusting element (8, 8 a) being displaceable relative to afurther adjusting element (8, 8 a) of a second inlet valve (9) or tofurther adjusting elements of further inlet valves of each cylinder theadjusting elements (8) are pivoting fingers or eccentrics and aremounted on a hollow shaft (6) that extends in direction of the inletvalves (9), the adjusting elements (8) of a first row of identical inletvalves (9) of all cylinders are fixed to the hollow shaft (6) by a rigidconnection, and when two inlet valves (9) are provided for eachcylinder, the adjusting elements (8 a) of a further row of adjacentidentical inlet valves (9) of all cylinders are rotatably mountedrelative to the hollow shaft (6), a further shaft (7) is arranged in abore (17) of the hollow shaft (6) for relative rotation thereto, whichfurther shaft (7) comprises an entraining element (19) for eachadjusting element (8 a) of the further row of identical inner valves(9), and said entraining element (19) projects through the hollow shaft(6) and is connected to the associated adjusting elements (8 a), thetransmission elements (5) have a two-part configuration comprising alever (5 a) having the first working surface (4) and at least oneratchet (5 b) having the second working surface (13), which ratchet (5b) is fixed with its fulcrum (11) on an end (10) of the lever (5 a)oriented toward the valve actuating elements (15), and the secondworking surface (13) adjoins a contact surface (14) of the valveactuating element (15), each ratchet (5 b) comprises a third workingsurface (12) for the respective adjusting element (8, 8 a) configured asa pivoting finger, said third working surface (12) extends on a sideoriented away from the second working surface (13) and scans a scanningcontour (9 a) of the adjusting element (8) during cam lift, whose lobeextends in opening direction of the inlet valve (9), the scanningcontour (9 a) being displaceable relative to the third working surface.